Example code on homepage does not compile

[xwu]

Describe the bug

A number of examples on the main site do not compile. Some appear to lack necessary import statements; others do not work in the currently released version of Swift.

The first example, under "Fast," crashes the compiler for at least one user, and produces the following compiler diagnostics for me in the REPL:

                        ˄˜˜˜     ˄
                        │        ╰─ error: generic parameter 'Scalar' could not be inferred
                        │        ╰─ note: explicitly specify the generic arguments to fix this issue
                        ╰─ error: cannot find type 'Span' in scope

To Reproduce

Steps to reproduce the behavior:

1. Go to swift.org
2. Scroll down to 'Fast'
3. Copy code and paste into Swift REPL
4. Observe compiler error

Expected behavior

Code should compile successfully.

Actual behavior

Code does not compile successfully.

Environment details

Desktop (please complete the following information):

• OS: macOS Sequoia 15.5
• Apple Swift version 6.1 (swift-6.1-RELEASE)

If possible, minimal yet complete reproducer code (or link to code)

// Vectorized check that a utf8 buffer is all ASCII
func isASCII(utf8: Span<SIMD16<UInt8>>) -> Bool {
  // combine all the code units into a single entry
  utf8.indices.reduce(into: SIMD16()) {
    // fold each set of code units into the result
    $0 |= utf8[$1]
  }
  // check that every entry is in the ASCII range
  .max() < 0x80
}

Swift.org version/commit hash

(?)

Additional context